Channel hole and bitline architecture and method to improve page or block size and performance of 3D NAND

ABSTRACT

Embodiments of a memory finger structure and architecture for a three-dimensional memory device and fabrication method thereof are disclosed. The method includes forming an alternating layer stack, forming a plurality of slit structures, forming a plurality of conductor/dielectric layer pairs, forming a first column of vertical memory strings, forming a second column of vertical memory strings, and forming a plurality of bitlines. The plurality of slit structures each extend vertically through the alternating layer stack and laterally along a wordline direction to divide the alternating layer stack into at least one memory finger. The vertical memory strings in the first column are displaced relative to each other along the wordline direction. The vertical memory strings in the second column are displaced relative to each other along the wordline direction. Each bitline is connected to an individual vertical memory string in the first and second columns.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/419,825, filed May 22, 2019, which is a continuation of InternationalApplication No. PCT/CN2019/075359, filed Feb. 18, 2019, which are herebyincorporated herein in their entireties by reference.

BACKGROUND

Embodiments of the present disclosure relate to three-dimensional (3D)memory devices and fabrication methods thereof. More specifically,embodiments of the present disclosure relate to charge trap flash (CTF)non-volatile memory devices, for example, 3D NAND devices.

Planar memory cells are scaled to smaller sizes by improving processtechnology, circuit design, programming algorithms, and fabricationprocesses. However, as feature sizes of a memory cell approach a lowerlimit, planar processes and fabrication techniques become challengingand costly. As a result, memory density for planar memory cellsapproaches an upper limit. 3D memory architecture can address thedensity limitation in planar memory cells. 3D memory architectureincludes a memory array and peripheral devices for controlling signalsto and from the memory array.

A 3D memory device includes one or more memory planes or memory stacks.Memory planes include one or more memory blocks or memory arrays. Memoryblocks include one or more addressable memory fingers. Memory fingersinclude two or more addressable memory pages. Generally, each memoryfinger requires two or more read operations to retrieve data from allmemory cells in each memory finger. Memory finger and memory page sizeis limited by the bitline (BL) pitch. A larger memory finger size leadsto longer wordlines (WL) and larger time constants, which leads toslower read times and longer total programming times.

BRIEF SUMMARY

Embodiments of memory finger structures and architectures for 3D memorydevices and fabrication methods thereof are disclosed herein.

Disclosed is a memory finger structure for a 3D memory device. In someembodiments, the 3D memory device includes an alternating layer stackdisposed on a first substrate. The alternating layer stack includes aplurality of conductor/dielectric layer pairs. The 3D memory devicefurther includes a first column of vertical memory strings extendingthrough the alternating layer stack and a first plurality of bitlinesdisplaced along a first direction and extending along a seconddirection. The first column of vertical memory strings is disposed at afirst angle relative to the second direction. Each of the firstplurality of bitlines is connected to an individual vertical memorystring in the first column. In some embodiments, the 3D memory device isa 3D NAND memory device.

In some embodiments, the 3D memory device further includes a secondcolumn of vertical memory strings extending through the alternatinglayer stack and a second plurality of bitlines displaced along the firstdirection and extending along the second direction. The second column ofvertical memory strings is disposed at a second angle relative to thesecond direction. Each of the second plurality of bitlines is connectedto an individual vertical memory string in the second column.

In some embodiments, the first and second columns define a channel holepitch along the first direction.

In some embodiments, the first plurality of bitlines and the secondplurality of bitlines define a bitline pitch.

In some embodiments, the channel hole pitch is about eight to abouttwelve times the bitline pitch. In some embodiments, the channel holepitch is about eight times the bitline pitch. In some embodiments, thechannel hole pitch is about ten times the bitline pitch. In someembodiments, the channel hole pitch is about twelve times the bitlinepitch. In some embodiments, the bitline pitch is 0.125 times the channelhole pitch. In some embodiments, the bitline pitch is 0.1 times thechannel hole pitch. In some embodiments, the bitline pitch is 0.083times the channel hole pitch.

In some embodiments, the first plurality of bitlines includes about fourto about six bitlines and the first column includes about four to aboutsix corresponding vertical memory strings. In some embodiments, thesecond plurality of bitlines includes about four to about six bitlinesand the second column includes about four to about six correspondingvertical memory strings. In some embodiments, the first plurality ofbitlines includes four bitlines and the first column includes fourcorresponding vertical memory strings, and the second plurality ofbitlines includes four bitlines and the second column includes fourcorresponding vertical memory strings. In some embodiments, the firstplurality of bitlines includes five bitlines and the first columnincludes five corresponding vertical memory strings, and the secondplurality of bitlines includes five bitlines and the second columnincludes five corresponding vertical memory strings. In someembodiments, the first plurality of bitlines includes six bitlines andthe first column includes six corresponding vertical memory strings, andthe second plurality of bitlines includes six bitlines and the secondcolumn includes six corresponding vertical memory strings.

In some embodiments, the first and second angles are equal. In someembodiments, the first and second angles are about 5 to about 30degrees.

In some embodiments, a number of the plurality of conductor/dielectriclayer pairs is at least 32.

In some embodiments, the 3D memory device further includes a pluralityof slit structures each extending vertically through the alternatinglayer stack and laterally along a wordline direction to divide thealternating layer stack into a plurality of memory fingers.

In some embodiments, the 3D memory device further includes a continuoustop select gate along the second direction and connected to the firstcolumn of vertical memory strings.

Another aspect of the present disclosure provides a method for forming amemory finger for a 3D memory device. In some embodiments, the methodincludes forming, on a first substrate, an alternating layer stack. Themethod further includes forming a plurality of slit structures eachextending vertically through the alternating layer stack and laterallyalong a wordline direction to divide the alternating layer stack into atleast one memory finger. The method further includes forming, in thealternating layer stack, a plurality of conductor/dielectric layerpairs. The method further includes forming a first column of verticalmemory strings extending through the alternating layer stack in the atleast one memory finger. The vertical memory strings in the first columnare displaced relative to each other along the wordline direction. Themethod further includes forming a second column of vertical memorystrings extending through the alternating layer stack in the at leastone memory finger. The vertical memory strings in the second column aredisplaced relative to each other along the wordline direction. Themethod further includes forming a plurality of bitlines displaced alongthe wordline direction and extending along a bitline direction in the atleast one memory finger, wherein each bitline is connected to anindividual vertical memory strings in the first and second columns. Insome embodiments, the 3D memory device is a 3D NAND memory device. Insome embodiments, forming the first and second columns can be donesimultaneously.

In some embodiments, forming the plurality of bitlines is by quadruplepatterning.

In some embodiments, the vertical memory strings of the first column aredisplaced evenly relative to each other along the wordline direction. Insome embodiments, the vertical memory strings of the second column aredisplaced evenly relative to each other along the wordline direction. Insome embodiments, the vertical memory strings of the first column aredisplaced relative to each other by a relative distance of about 1 nm toabout 10 nm. In some embodiments, the vertical memory strings of thesecond column are displaced relative to each other by a relativedistance of about 1 nm to about 10 nm.

In some embodiments, the method further includes a continuous top selectgate along the bitline direction and connected to the first and secondcolumns of vertical memory strings in the at least one memory finger.

Other aspects of the present disclosure can be understood by thoseskilled in the art in light of the description, the claims, and thedrawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate embodiments of the present disclosureand, together with the description, further serve to explain theprinciples of the present disclosure and to enable a person skilled inthe pertinent art to make and use the present disclosure.

FIG. 1 illustrates a schematic diagram of an exemplary 3D memory devicein a plan view, according to some embodiments of the present disclosure.

FIG. 2 illustrates a schematic enlarged plan view of a region of 3Dmemory device including an exemplary bitline through array contactregion, according to some embodiments of the present disclosure.

FIG. 3 illustrates a schematic plan view of an exemplary channel hole,according to some embodiments of the present disclosure.

FIG. 4 illustrates a schematic cross-sectional diagram of an exemplary3D memory device including a vertical string of memory cells, accordingto some embodiments of the present disclosure.

FIGS. 5A-5B illustrate schematic cross-sectional views of an exemplary3D memory device at certain fabricating stages, according to someembodiments of the present disclosure.

FIGS. 6A-6B are flowcharts of an exemplary method for forming anexemplary 3D memory device, according to some embodiments of the presentdisclosure.

FIG. 7 illustrates a schematic enlarged plan view of a region of anexemplary 3D memory device, according to some embodiments of the presentdisclosure.

FIGS. 8A-8B illustrate schematic enlarged plan views of a region of anexemplary 3D memory device, according to some embodiments of the presentdisclosure.

FIG. 9 illustrates a schematic enlarged plan view of a region of anexemplary 3D memory device, according to some embodiments of the presentdisclosure.

FIG. 10 is a flowchart of an exemplary method for forming an exemplary3D memory device, according to some embodiments of the presentdisclosure.

Embodiments of the present disclosure will be described with referenceto the accompanying drawings.

DETAILED DESCRIPTION

Although specific configurations and arrangements are discussed, itshould be understood that this is done for illustrative purposes only. Aperson skilled in the pertinent art will recognize that otherconfigurations and arrangements can be used without departing from thespirit and scope of the present disclosure. It will be apparent to aperson skilled in the pertinent art that the present disclosure can alsobe employed in a variety of other applications.

It is noted that references in the specification to “one embodiment,”“an embodiment,” “an example embodiment,” “some embodiments,” etc.,indicate that the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases do not necessarily refer to the same embodiment. Further,when a particular feature, structure or characteristic is described inconnection with an embodiment, it would be within the knowledge of aperson skilled in the pertinent art to effect such feature, structure orcharacteristic in connection with other embodiments whether or notexplicitly described.

In general, terminology may be understood at least in part from usage incontext. For example, the term “one or more” as used herein, dependingat least in part upon context, may be used to describe any feature,structure, or characteristic in a singular sense or may be used todescribe combinations of features, structures, or characteristics in aplural sense. Similarly, terms, such as “a,” “an,” or “the,” again, maybe understood to convey a singular usage or to convey a plural usage,depending at least in part upon context.

It should be readily understood that the meaning of “on,” “above,” and“over” in the present disclosure should be interpreted in the broadestmanner such that “on” not only means “directly on” something but alsoincludes the meaning of “on” something with an intermediate feature or alayer therebetween, and that “above” or “over” not only has the meaningof “above” or “over” something but can also include the meaning it is“above” or “over” something with no intermediate feature or layertherebetween (i.e., directly on something).

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

As used herein, the term “substrate” refers to a material onto whichsubsequent material layers are added. The substrate itself can bepatterned. Materials added on top of the substrate can be patterned orcan remain unpatterned. Furthermore, the substrate can include a widearray of semiconductor materials, such as silicon, germanium, galliumarsenide, indium phosphide, etc. Alternatively, the substrate can bemade from an electrically non-conductive material, such as a glass, aplastic, or a sapphire wafer.

As used herein, the term “layer” refers to a material portion includinga region with a thickness. A layer can extend over the entirety of anunderlying or overlying structure, or may have an extent less than theextent of an underlying or overlying structure. Further, a layer can bea region of a homogeneous or inhomogeneous continuous structure that hasa thickness less than the thickness of the continuous structure. Forexample, a layer can be located between any pair of horizontal planesbetween, or at, a top surface and a bottom surface of the continuousstructure. A layer can extend horizontally, vertically, and/or along atapered surface. A substrate can be a layer, can include one or morelayers therein, and/or can have one or more layer thereupon, thereabove,and/or therebelow. A layer can include multiple layers. For example, aninterconnection layer can include one or more conductor and contactlayers (in which contacts, interconnect lines, and/or vias are formed)and one or more dielectric layers.

As used herein, the term “nominal/nominally” refers to a desired, ortarget, value of a characteristic or parameter for a component or aprocess operation, set during the design phase of a product or aprocess, together with a range of values above and/or below the desiredvalue. The range of values can be due to slight variations inmanufacturing processes or tolerances. As used herein, the term “about”indicates the value of a given quantity that can vary based on aparticular technology node associated with the subject semiconductordevice. Based on the particular technology node, the term “about” canindicate a value of a given quantity that varies within, for example,10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

As used herein, the term “3D memory device” refers to a semiconductordevice with vertically-oriented strings of memory cell transistors(i.e., region herein as “memory strings,” such as NAND strings) on alaterally-oriented substrate so that the memory strings extend in thevertical direction with respect to the substrate. As used herein, theterm “vertical/vertically” means nominally perpendicular to a lateralsurface of a substrate.

Various embodiments in accordance with the present disclosure provide a3D memory device with through array contact (TAC) structures for amemory array (also referred to herein as an “array device”). The TACstructures allow contacts between the memory and various peripheralcircuits and/or peripheral devices (e.g., page buffers, latches,decoders, etc.) to be fabricated in a limited number of steps (e.g., ina single step or in two steps), thereby reducing the process complexityand manufacturing cost. The disclosed TACs are formed through a stack ofalternating dielectric layers, which can be more easily etched to formthrough holes therein compared with a stack of alternating conductor anddielectric layers.

The TACs can provide vertical interconnects between the stacked arraydevice and peripheral device (e.g., for power bus and metal routing),thereby reducing metal levels and shrinking die size. In someembodiments, the TACs can be interconnected with various lines in a topconductive layer and/or a bottom conductive layer, which are suitablefor those 3D memory architectures in which the array device and theperipheral device formed on different substrates are formed sequentiallyor joined by hybrid bonding in a face-to-face manner. In someembodiments, the TACs in the through array contact structures disclosedherein are formed through a stack of alternating dielectric layers,which can be more easily etched to form through holes therein comparedwith a stack of alternating conductor and dielectric layers, therebyreducing the process complexity and manufacturing cost.

FIG. 1 illustrates a schematic diagram of an exemplary 3D memory device100 in a plan view, according to some embodiments of the presentdisclosure. 3D memory device 100 can include a plurality of channelstructure regions (e.g., memory planes, memory blocks, memory fingers,etc., which are described in detail in connection with various figuresbelow), while one or more TAC structures can be formed between twoneighboring channel structure regions (e.g., two channel structureregions next to each other).

As shown in FIG. 1 , 3D memory device 100 can include four or morememory planes 110, each of which can include a plurality of memoryblocks 115. It is noted that, the arrangement of memory planes 110 in 3Dmemory device 100 and the arrangement of memory blocks 115 in eachmemory plane 110 illustrated in FIG. 1 are only used as an example,which is not limit the scope of the present disclosure.

TAC structures can include one or more bitline (BL) TAC regions 160 thatare sandwiched by two neighboring memory blocks 115 in the bitlinedirection of the 3D memory device (labeled as “BL” in figures) andextended along the wordline direction of the 3D memory device (labeledas “WL” in figures), one or more wordline (WL) TAC regions 170 that aresandwiched by two neighboring memory blocks 115 in the wordlinedirection (WL) and extended along the bitline direction (BL), and one ormore staircase structure (SS) TAC regions 180 that are located at theedges of each memory plane 110.

In some embodiments, 3D memory device 100 can include a plurality ofcontact pads 120 arranged in a line at an edge of the 3D memory device100. Contact pads 120 can be used for electrically interconnecting 3Dmemory device 100, for example, metal interconnections, to any suitabledevice and/or interface that can provide driving power, receive controlsignals, transmit response signals, etc.

FIG. 2 depicts an enlarged plan view of a region 130 shown in FIG. 1including an exemplary bitline (BL) TAC region 160 of the 3D memorydevice 100.

Referring to FIG. 2 , an enlarged plan view of the region 130 shown inFIG. 1 including an exemplary bitline (BL) TAC region of the 3D memorydevice 100 is illustrated, according to some embodiments of the presentdisclosure. The region 200 of the 3D memory device 100 (i.e., region 130as shown in FIG. 1 ) can include two channel structure regions 210(e.g., neighboring memory blocks 115 in BL direction) and a bitline (BL)TAC region 233 (e.g., BL TAC region 160 as shown in FIG. 1 ).

Channel structure regions 210 can include an array of channel structures212, each being part of a NAND string including a plurality of stackedmemory cells. Channel structures 212 extend through a plurality ofconductive layer and dielectric layer pairs that are arranged along adirection that is perpendicular to the plan view, which is also referredas a direction that is perpendicular to the surface of the substrate ofthe 3D memory device, and/or a “vertical direction” (which isillustrated in a cross-sectional view in connection with FIGS. 5A-5Bdescribed in detail below).

The plurality of conductor/dielectric layer pairs are also referred toherein as an “alternating conductor/dielectric stack.” The number of theconductor/dielectric layer pairs in alternating conductor/dielectricstack (e.g., 32, 64, or 96) can set the number of memory cells in 3Dmemory device 100. Conductive layers and dielectric layers inalternating conductor/dielectric stack alternate in the verticaldirection. In other words, except layer pairs at the top or bottom ofalternating conductor/dielectric stack, each conductive layer can beadjoined by two dielectric layers on both sides, and each dielectriclayer can be adjoined by two conductive layers on both sides.

Conductive layers can include conductive materials including, but notlimited to, tungsten (W), cobalt (Co), copper (Cu), aluminum (Al),polycrystalline silicon (polysilicon), doped silicon, silicides, or anycombination thereof. Dielectric layers can include dielectric materialsincluding, but not limited to, silicon oxide, silicon nitride, siliconoxynitride, or any combination thereof. In some embodiments, conductivelayers include metal layers, such as W, and dielectric layers includesilicon oxide.

In some embodiments, BL TAC region 233 can be sandwiched by twoneighboring channel structure regions 210 in BL direction and can extendin WL direction. TAC region 233 can be defined by a barrier structure224 in conjunction with the edges of BL TAC region 233 of 3D memorydevice 100. Multiple TACs 226 can be formed in BL TAC region 233, whichis enclosed laterally by barrier structure 224 and the edges of BL TACregion 233. In some embodiments, multiple TACs 226 in BL TAC region 233can penetrate an alternating dielectric stack for switch routing and forreducing bitline capacitance.

The alternating dielectric stack can include a plurality of dielectriclayer pairs that are arranged along the vertical direction that isperpendicular to the surface of the substrate of the 3D memory device(which is illustrated in a cross-sectional view in connection with FIGS.5A-5B described in detail below). Each dielectric layer pair includes afirst dielectric layer and a second dielectric layer that is differentfrom first dielectric layer. In some embodiments, first dielectric layerand second dielectric layer each includes silicon nitride and siliconoxide. First dielectric layers in alternating dielectric stack can bethe same as dielectric layers in the alternating conductor/dielectricstack described above. In some embodiments, the number of dielectriclayer pairs in the alternating dielectric stack is the same as thenumber of the conductor/dielectric layer pairs in the alternatingconductor/dielectric stack.

As shown in FIG. 2 , each channel structure region 210 can include oneor more slit structures 214 each extending along WL direction. At leastsome slit structures 214 can function as a common source contact for anarray of channel structures 212 in channel structure regions 210. Slitstructures 214 can also divide 3D memory device 100 into multiple memoryfingers 242 and/or dummy memory fingers 246. A top select gate cut 255can be disposed along a centerline of each memory finger 242 along WLdirection to divide a top select gate (TSG) of memory finger 242 intotwo portions (e.g., two memory pages). The top select gate cut 255 caninclude dielectric materials including, but not limited to, siliconoxide, silicon nitride, silicon oxynitride, or any combination thereof.

In some embodiments, dummy channel structures 222 can be formed in partof channel structure regions 210, for example, in dummy memory fingers246 that are adjacent to BL TAC region 233 along BL direction. Dummychannel structures 222 can provide mechanical support for the memoryarray structures. Dummy memory fingers 246 do not have memory functionsand, thus, bitlines and related interconnection lines are not formed indummy memory fingers 246.

Referring to FIG. 3 , a schematic plan view of a channel structure 212shown in FIG. 2 is illustrated, according to some embodiments of thepresent disclosure.

As shown in FIG. 3 , channel hole 300 (i.e., channel structure 212 asshown in FIG. 2 ) can include a channel 302, a first insulating layer304, a charge trap layer 306, and a second insulating layer 308. Channelhole 300 is a filled hole or cylinder extending vertically through thealternating conductor/dielectric stack of 3D memory device 100 to form avertical memory string of a plurality of memory cells, for example, aNAND memory string. Channel hole 300 can have an ellipticalcross-section, for example, a circular cross-section. First insulatinglayer 304 is radially disposed between channel 302 and charge trap layer306, and charge trap layer 306 is radially disposed between firstinsulating layer 304 and second insulating layer 308. Channel 302 iselectrically connected to a bitline (BL) connection at one end ofchannel hole 300, which transfers charge (i.e., electrons) along channel302. First insulating layer 304 functions as a tunneling layer forcharge (i.e., electrons) along channel 302. Charge trap layer 306functions as a charge trap layer to store charge (i.e., electrons).Second insulating layer 308 functions as a blocking layer or gate and iselectrically connected to a plurality of wordline (WL) connectionsspaced vertically along channel hole 300. In some embodiments, channelhole 300 can be a plurality of vertical memory strings. In someembodiments, channel hole 300 can be a vertical memory string of aplurality of memory cells.

In some embodiments, channel 302 can include conductive materials. Forexample, channel 302 can include conductive materials including, but notlimited to, tungsten (W), cobalt (Co), copper (Cu), aluminum (Al),polycrystalline silicon (polysilicon), doped silicon, silicides, or anycombination thereof. In some embodiments, channel 302 can includeconductive and insulating materials. For example, channel 302 can bepolysilicon annular ring with an insulating (e.g., oxide) centerextending along the length of channel hole 300. In some embodiments,first insulating layer 304 can be silicon oxide. In some embodiments,charge trap layer 306 can be silicon nitride. In some embodiments,second insulating layer 308 can be silicon oxide.

FIG. 4 depicts a schematic cross-sectional diagram of a region 260 shownin FIG. 2 including a plurality of channel structures 212 (i.e., channelhole 300 as shown in FIG. 3 ) along a Y-direction (e.g., verticaldirection of 3D memory device 100) forming a vertical string of memorycells, according to some embodiments of the present disclosure. It isnoted that X-direction (e.g., WL direction) and Y-direction axes areshown in FIG. 4 to illustrate the spatial relationship of the pluralityof channel structures 212.

As shown in FIG. 4 , region 400 of 3D memory device 100 (i.e., region260 as shown in FIG. 2 ) can include a plurality of bitlines (BL) 402a-402 h connected to a top end of a plurality of channel holes 404 a-404h (i.e., eight parallel channel structures 212 of region 260 as shown inFIG. 2 , e.g., channel hole 300 as shown in FIG. 3 ), respectively, toform a plurality of memory strings. The plurality of channel holes 404a-404 h are each connected to a plurality of top select gates (TSG) 406a-406 h, respectively, along the X-direction. The plurality of channelholes 404 a-404 h are each connected to a plurality of wordlines (WL)410, 411, 412, . . . , 474. The plurality of wordlines (WL) 410, 411,412, . . . , 474 each extend along the X-direction and are spacedvertically along the Y-direction and connect to the plurality of channelholes 404 a-404 h. As shown in FIG. 4 , for example, 3D memory device100 can include 64 layers. A bottom end of the plurality of channelholes 404 a-404 h can be connected to a ground select line (GSL) 408. Insome embodiments, channel holes 404 a-404 h can each be a plurality ofvertical memory strings. In some embodiments, channel holes 404 a-404 hcan each be a vertical memory string of a plurality of memory cells.

Referring to FIGS. 5A-5B, schematic cross-sectional views of anexemplary 3D memory device at certain fabricating stages are shown,according to some embodiments of the present disclosure. FIG. 5Aillustrates two separate chips 500A, 500B before bonding, while FIG. 5Billustrates 3D memory device 500C that is formed by bonding first chip500A and second chip 500B. It is noted that 3D memory device 500C shownin FIG. 5B can be part of a non-monolithic 3D memory device, in whichcomponents (e.g., the peripheral device and array device) can be formedseparately on different substrates. For example, 3D memory device 500Ccan be region 130 described above in connection with FIG. 1 .

As shown in FIG. 5A, first chip 500A can include a first substrate 570and an array device above first substrate 570. It is noted thatX-direction and Y-direction axes, similar to X-direction and Y-directionaxes shown in FIG. 4 , are shown in FIGS. 5A and 5B to furtherillustrate the spatial relationship of the components in chips 500A and500B, as well as 3D memory device 500C. First substrate 570 includes afirst bonding surface 534, which can be a lateral bottom surfaceextending laterally in the X-direction (the lateral direction, e.g., WLdirection or BL direction).

As used herein, whether one component (e.g., a layer or a device) is“on,” “above,” or “below” another component (e.g., a layer or a device)of a semiconductor device (e.g., array device) is determined relative tothe substrate of the semiconductor device (e.g., first substrate 570) inthe Y-direction (i.e., vertical direction) when the substrate ispositioned (or otherwise disposed) in the lowest plane of thesemiconductor device in the Y-direction. The cross-sectional view of the3D memory device shown in FIGS. 5A and 5B is along a plane in BLdirection and Y-direction.

First substrate 570 can be used for supporting the array device, and caninclude an array interconnection layer 530 and a base substrate 540.Array interconnection layer 530 can be a back-end-of-line (BEOL)interconnection layer including one or more interconnection structures532 embedded in a dielectric layer. Interconnection structures 532 caninclude, but are not limited to, contacts, single-layer/multi-layervias, conductive lines, plugs, pads, and/or any other suitableconductive structures including, but not limited to, tungsten (W),cobalt (Co), copper (Cu), aluminum (Al), polycrystalline silicon(polysilicon), doped silicon, silicides, or any combination thereof. Thedielectric layer can include dielectric materials including, but notlimited to, silicon oxide, silicon nitride, silicon oxynitride, or anycombination thereof. One or more portions of interconnection structures532 can be exposed on the first bonding surface 534 of first substrate570.

Base substrate 540 can include any suitable semiconductor including, butnot limited to, silicon (e.g., monocrystalline silicon, polycrystallinesilicon), silicon germanium (SiGe), gallium arsenide (GaAs), germanium(Ge), silicon on insulator (SOI), germanium on insulator (GOI), or anysuitable combination thereof. In some embodiments, base substrate 540 isa thinned substrate (e.g., a semiconductor layer), which was thinned bygrinding, wet/dry etching, chemical mechanical polishing (CMP), or anycombination thereof. In some embodiments, base substrate 540 can be asingle layer substrate or a multi-layer substrate, for example, amonocrystalline single-layer substrate, a polycrystalline silicon(polysilicon) single-layer substrate, a polysilicon and metalmulti-layer substrate, etc.

Further, one or more openings 542 can be formed in regions of basesubstrate 540 that correspond to one or more through array contact (TAC)structures 526 of the array device. In some embodiments, a plurality ofTACs 526 can extend through one or more openings 542 to electricallyconnect to one or more interconnection structures 532 in arrayinterconnection layer 530. In some embodiments, a plurality ofconductive plugs (not shown) penetrating through the one or moreopenings 542 can be used to electrically connect the plurality of TACs526 to one or more interconnection structures 532 in arrayinterconnection layer 530. In some embodiments, one or more openings 542can be filled with dielectric material to insulate the plurality of TACs526 and/or plurality of conductive plugs.

In some embodiments, array device can be a NAND flash memory device, inwhich memory cells are provided in the form of an array of channelstructures (not shown in FIGS. 5A and 5B) extending along theY-direction above first substrate 570. The array device can include aplurality of channel structures that extend through an alternatingconductor/dielectric stack 580, including a plurality of conductivelayer 580A and dielectric layer 580B pairs. The number of theconductor/dielectric layer pairs in alternating conductor/dielectricstack 580 (e.g., 32, 64, or 96) can define the number of memory cells in3D memory device 500C.

Conductive layers 580A and dielectric layers 580B in alternatingconductor/dielectric stack 580 alternate along the Y-direction. As shownin FIG. 5A, except a top or a bottom end layer of alternatingconductor/dielectric stack 580, each conductive layer 580A can beadjoined vertically by two dielectric layers 580B (i.e., one above andone below conductive layer 580A), and each dielectric layer 580B can beadjoined vertically by two conductive layers 580A (i.e., one above andone below dielectric layer 580B). Conductive layers 580A can each havethe same thickness or different thicknesses. Similarly, dielectriclayers 580B can each have the same thickness or different thicknesses.Conductive layers 580A can include conductive materials including, butnot limited to, tungsten (W), cobalt (Co), copper (Cu), aluminum (Al),polycrystalline silicon (polysilicon), doped silicon, silicides, or anycombination thereof. Dielectric layers 580B can include dielectricmaterials including, but not limited to, silicon oxide, silicon nitride,silicon oxynitride, or any combination thereof. In some embodiments,conductive layers 580A include metal layers, such as W, and dielectriclayers 580B include silicon oxide.

In some embodiments, the array device further includes slit structures514. Each slit structure 514 can extend along the Y-direction throughalternating conductor/dielectric stack 580. Slit structure 514 can alsoextend laterally (i.e., substantially parallel to the substrate) toseparate alternating conductor/dielectric stack 580 into multiple blocks(e.g., memory block 115 as shown in FIG. 1 in plan view). Slit structure514 can include a slit filled with conductive materials including, butnot limited to, W, Co, Cu, Al, silicides, or any combination thereof.Slit structure 514 can further include a dielectric layer with anysuitable dielectric materials between the filled conductive materialsand alternating conductor/dielectric stack 580 to electrically insulatethe filled conductive materials from surrounding conductive layers 580Ain alternating conductor/dielectric stack 580. As a result, slitstructures 514, similar to slit structure 214 as shown in FIG. 2 , canseparate 3D memory device 500A, 500B, 500C into multiple memory fingers(e.g., memory finger 242 as shown in FIG. 2 in plan view).

In some embodiments, slit structure 514 functions as the source contactfor channel structures in the same memory finger that share the samearray common source. Slit structure 514 can thus be referred to as a“common source contact” of multiple channel structures. In someembodiments, base substrate 540 includes a doped region 544 (includingp-type or n-type dopants at a desired doping level), and a bottom end ofslit structure 514 contacts doped region 544 of base substrate 540.

In some embodiments, an alternating dielectric stack 560 can be locatedin a region that is surrounded laterally by a barrier structure 516 onbase substrate 540. Alternating dielectric stack 560 can include aplurality of dielectric layer pairs. For example, alternating dielectricstack 560 can be formed by an alternating stack of a first dielectriclayer 560A and a second dielectric layer 560B that is different fromfirst dielectric layer 560A. In some embodiments, first dielectric layer560A includes silicon nitride and second dielectric layer 560B includessilicon oxide. In some embodiments, second dielectric layers 560B inalternating dielectric stack 560 can be the same as dielectric layers580B in alternating conductor/dielectric stack 580. In some embodiments,the number of dielectric layer pairs in alternating dielectric stack 560can be the same as the number of conductor/dielectric layer pairs inalternating conductor/dielectric stack 580.

In some embodiments, barrier structure 516 can extend along theY-direction to separate laterally alternating conductor/dielectric stack580 and alternating dielectric stack 560. For example, barrier structure516 can be a boundary between alternating conductor/dielectric stack 580and alternating dielectric stack 560. In some embodiments, alternatingdielectric stack 560 can be enclosed laterally by at least barrierstructure 516. In some embodiments, barrier structure 516 can form aclosed shape (e.g., a rectangle, a square, a circle, etc.) in plan viewto completely enclose alternating dielectric stack 560.

As shown in FIG. 5A, first chip 500A further includes a plurality ofTACs 526 each extending along the Y-direction through alternatingdielectric stack 560. TACs 526 can be formed only inside the areaenclosed laterally by at least barrier structure 516, which includes aplurality of dielectric layer pairs. For example, TACs 526 can extendvertically through dielectric layers (e.g., first dielectric layers 560Aand second dielectric layers 560B), but not through any conductivelayers (e.g., conductive layers 580A). Each TAC 526 can extend throughthe entire thickness of alternating dielectric stack 560, (e.g., all thedielectric layer pairs along the Y-direction). In some embodiments, TACs526 can extend through base substrate 540 through opening 542 andelectrically contact interconnection structure 532.

In some embodiments, TACs 526 can carry electrical signals to and/orfrom the array device, for example, as part of a power bus withshortened interconnect routing. In some embodiments, TACs 526 canprovide electrical connections between the array device and theperipheral devices (not shown in FIGS. 5A and 5B) through one or moreinterconnection structures 532. In some embodiments, TACs 526 canprovide mechanical support to alternating dielectric stack 560. Forexample, each TAC 526 can include a vertical opening through alternatingdielectric stack 560 that is filled with conductive materials,including, but not limited to, W, Co, Cu, Al, doped silicon, silicides,or any combination thereof.

Second chip 500B can include a second substrate 510 and a peripheralinterconnection layer 520 on the second substrate 510. Second substrate510 can include any suitable semiconductor including, but not limitedto, silicon (e.g., monocrystalline silicon, polycrystalline silicon),silicon germanium (SiGe), gallium arsenide (GaAs), germanium (Ge),silicon on insulator (SOI), germanium on insulator (GOI), or anysuitable combination thereof. Second substrate 510 can be a single layersubstrate or a multi-layer substrate, for example, a monocrystallinesingle-layer substrate, a polycrystalline silicon (polysilicon)single-layer substrate, a polysilicon and metal multi-layer substrate,etc. In some embodiments, second substrate 510 is a thinned substrate(e.g., a semiconductor layer), which was thinned by grinding, wet/dryetching, chemical mechanical polishing (CMP), or any combinationthereof.

One or more peripheral circuits (not shown in FIGS. 5A and 5B) can beformed on the second substrate 510. The one or more peripheral circuitscan include any suitable digital, analog, and/or mixed-signal peripheralcircuits used for facilitating the operation of the 3D memory device.For example, the one or more peripheral circuits can include a pagebuffer, a decoder (e.g., a row decoder and a column decoder), a latch, asense amplifier, a driver, a charge pump, a current or voltagereference, any active or passive components of the circuits (e.g.,transistors, diodes, resistors, or capacitors), or any combinationthereof. In some embodiments, the one or more peripheral circuits can beformed on second substrate 510 using complementarymetal-oxide-semiconductor (CMOS) technology (also known as a “CMOSchip”).

In some embodiments, peripheral interconnection layer 520 can includeone or more interconnection structures 522 embedded in a dielectriclayer for electrically connecting the one or more peripheral circuits tothe array device above the first substrate 570. The one or moreinterconnection structures 522 can include any suitable conductivestructures including, but not limited to, contacts,single-layer/multi-layer vias, conductive layer(s), plugs, pads, and/orany other suitable conductive structures that are made by conductivematerials including, but not limited to, W, Co, Cu, Al, doped silicon,silicides, or any combination thereof. Dielectric layer of peripheralinterconnection layer 520 can have a single-layer structure or amulti-layer structure and include dielectric materials including, butnot limited to, silicon oxide, silicon nitride, silicon oxynitride,doped silicon oxide, or any combination thereof.

Second chip 500B can include a second bonding surface 524, which can bea lateral top surface extending laterally along the X-direction (thelateral direction, e.g., WL direction or BL direction). In someembodiments, first bonding surface 534 of first chip 500A is bonded tosecond bounding surface 524 of second chip 500B. For example, peripheralinterconnection layer 520 and array interconnection layer 530 can bebonded in a face-to-face manner. As shown in FIG. 5B, first chip 500Aand second chip 500B can be bonded at bonding interface 555 to form 3Dmemory device 500C.

In some embodiments, bonding interface 555 is between peripheralinterconnection layer 520 and array interconnection layer 530. Forexample, bonding interface 555 can be between two dielectric layers,such as a silicon nitride layer and a silicon oxide layer. For example,bonding interface 555 can be between two conductive layers, such as twometal (e.g., Cu) layers. In some embodiments, the bonding interfaceincludes both the interface between dielectric layers and the interfacebetween conductive layers. In some embodiments, one or moreinterconnection structures 532 in first chip 500A and one or moreinterconnection structures 522 in second chip 500B can be contacted witheach other at bonding interface 555 for electrically interconnecting oneor more TACs 526 in first chip 500A and the peripheral circuits insecond chip 500B.

Bonding interface 555 can be formed by chemical bonds between thedielectric layers and/or the conductive layers on both sides of thebonding interface, e.g. first bonding surface 534 and second bondingsurface 524 as shown in FIG. 5A. Bonding interface 555 can be formed byphysical interaction (e.g., inter-diffusion) between the dielectriclayers and/or the conductive layers on both sides of the bondinginterface. In some embodiments, the bonding interface is formed after aplasma treatment or a thermal treatment of the surfaces from both sidesof the bonding interface prior to the bonding process.

By using the bonding through contact hole on the back side of the firstsubstrate, a pad layer of the interconnection structures can be formedon the back surface of the first substrate corresponding to the arraydevice. Since the pad layer is formed on the back surface of the firstsubstrate rather than the surrounding regions of the first substrate,the size of the 3D memory device can be reduced and the integrationdegree of the 3D memory device can be increased.

Referring to FIGS. 6A-6B, schematic flowcharts of an exemplary methodfor forming a 3D memory device are illustrated, according to someembodiments of the present disclosure. It should be understood that theoperations shown in FIGS. 6A-6B are not exhaustive and that otheroperations can be performed as well before, after, or between any of theillustrated operations.

Referring to FIG. 6A, a flowchart of an exemplary method 600A forforming an array device and an array interconnection layer isillustrated, according to some embodiments. As shown in FIG. 6A, method600A starts at operation 604, in which an alternating dielectric stackis formed on a first substrate. In some embodiments, the first substratecan be any suitable semiconductor substrate having any suitablestructure, such as a monocrystalline single-layer substrate, apolycrystalline silicon (polysilicon) single-layer substrate, apolysilicon and metal multi-layer substrate, etc.

A plurality of dielectric layer pairs (also referred to herein as an“alternating dielectric stack”) can be formed on the first substrate.The alternating dielectric stack can include an alternating stack of afirst dielectric layer and a second dielectric layer that is differentfrom first dielectric layer. In some embodiments, each dielectric layerpair includes a layer of silicon nitride and a layer of silicon oxide.In some embodiments, there are more layers than the dielectric layerpairs made of different materials and with different thicknesses inalternating dielectric stack. The alternating dielectric stack can beformed by one or more thin film deposition processes including, but notlimited to, chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), or any combination thereof.

Method 600A proceeds to operation 606, in which a staircase structure isformed at one or more edges of the alternating dielectric stack. In someembodiments, a trim-etch process can be performed on at least one side(in the lateral direction) of alternating dielectric stack to form thestaircase structure with multiple levels. Each level can include one ormore dielectric layer pairs with alternating first dielectric layer andsecond dielectric layer.

Method 600A proceeds to operation 608, in which a plurality of channelstructures and one or more barrier structures are formed. Each channelstructure and each barrier structure can extend vertically through thealternating dielectric stack.

In some embodiments, fabrication processes to form the channelstructures include forming a channel hole that extends verticallythrough the alternating dielectric stack by, for example, wet etchingand/or dry etching. In some embodiments, fabrication processes to formthe channel structures further include forming a semiconductor channeland a memory film between the semiconductor channel and the dielectriclayer pairs in the alternating dielectric stack. The semiconductorchannel can include semiconductor materials, such as polysilicon. Thememory film can be a composite dielectric layer, such as a combinationof a tunneling layer, a storage layer, and a blocking layer.

The tunneling layer can include dielectric materials including, but notlimited to, silicon oxide, silicon nitride, silicon oxynitride, or anycombination thereof. Electrons or holes from the semiconductor channelcan tunnel to a storage layer through the tunneling layer. The storagelayer can include materials for storing charge for memory operation. Thestorage layer materials include, but are not limited to, siliconnitride, silicon oxynitride, a combination of silicon oxide and siliconnitride, or any combination thereof. The blocking layer can includedielectric materials including, but not limited to, silicon oxide or acombination of silicon oxide/silicon nitride/silicon oxide (ONO). Theblocking layer can further include a high-k dielectric layer, such as analuminum oxide (Al₂O₃) layer. Semiconductor channel and memory film canbe formed by one or more thin film deposition processes, such as ALD,CVD, PVD, any other suitable processes, or any combination thereof.

In some embodiments, fabrication processes to form barrier structuresare similarly and simultaneously performed as the fabrication processesto form channel structures, thereby reducing fabrication complexity andcost. In some other embodiments, channel structures and barrierstructures are formed in different fabrication steps so that barrierstructures can be filled with materials different from the materialsfilling channel structures.

In some embodiments, fabrication processes to form a barrier structureinclude forming a trench that extends vertically through alternatingdielectric stack by, for example, wet etching and/or dry etching. Afterthe trench is formed through the alternating dielectric stack, one ormore thin film deposition processes can be performed to fill the trenchwith dielectric materials including, but not limited to, silicon oxide,silicon nitride, silicon oxynitride, silicon oxide/siliconnitride/silicon oxide (ONO), aluminum oxide (Al₂O₃), or any combinationthereof.

By forming the one or more barrier structures, the alternatingdielectric stack can be separated into two types of regions: one or moreinside regions each enclosed laterally by at least a barrier structure(in conjunction with the edge(s) of alternating dielectric stack in someembodiments) and an outside region in which channel structures and/orword line contacts can be formed. It is noted that, each inside regioncorresponds to an opening in the first substrate.

In some embodiments, at least one inside region can be used to form a BLTAC structure as described above in connection with FIG. 2 . As such,the barrier structure enclosing such inside region can include twoparallel barrier walls that extend along WL direction.

In some embodiments, dummy channel structures can be formedsimultaneously with channel structures. The dummy channel structures canextend vertically through the alternating layer stack and can be filledwith the same materials as those in the channel structures. Differentfrom the channel structures, contacts are not formed on the dummychannel structures to provide electrical connections with othercomponents of the 3D memory device. Thus, the dummy channel structuresare not used for forming memory cells in the 3D memory device.

Method 600A proceeds to operation 610, in which a plurality of slits areformed and first dielectric layers in a portion of the alternatingdielectric stack are replaced with conductive layers through theplurality of slits. For example, multiple parallel slits extending inthe WL direction can be first formed by wet etching and/or dry etchingof dielectrics (e.g., silicon oxide and silicon nitride) through thealternating dielectric stack in the outside area. In some embodiments,doped regions can then be formed in the first substrate under each slitby, for example, ion implantation and/or thermal diffusion through theslits. It is understood that doped regions can be formed in an earlierfabrication stage, for example, prior to the formation of the slits,according to some embodiments.

In some embodiments, the formed slits are used for a gate replacementprocess (also known as the “word line replacement” process) thatreplaces, in the outside area of alternating dielectric stack, firstdielectric layers (e.g., silicon nitride) with conductive layers (e.g.,W). It is noted that the gate replacement occurs only in the outsidearea of the alternating dielectric stack, but not in the inside area,due to the formation of barrier structure. Barrier structure can preventthe etching of first dielectric layers (e.g., silicon nitride) in theinside area of alternating dielectric stack since barrier structure canbe filled with materials immune to the etching step of the gatereplacement process.

As a result, after the gate replacement process, the alternatingdielectric stack in the outside region becomes the alternatingconductor/dielectric stack. The replacement of first dielectric layerswith conductive layers can be performed by wet etching first dielectriclayers (e.g., silicon nitride) selective to second dielectric layers(e.g., silicon oxide) and filling the structure with conductive layers(e.g., W). Conductive layers can be filled by PVD, CVD, ALD, any othersuitable process, or any combination thereof. Conductive layers caninclude conductive materials including, but not limited to, W, Co, Cu,Al, polysilicon, silicides, or any combination thereof. The formedalternating conductor/dielectric stack and remaining alternatingdielectric stack can constitute an alternating stack.

Method 600A proceeds to operation 612, in which slit structures areformed by filling (e.g., depositing) conductive materials into the slitsby PVD, CVD, ALD, any other suitable process, or any combinationthereof. Slit structures can include conductive materials including, butnot limited to, W, Co, Cu, Al, polysilicon, silicides, or anycombination thereof. In some embodiments, a dielectric layer (e.g., asilicon oxide layer) is formed first between the conductive materials ofslit structure and conductive layers surrounding slit structure in thealternating conductor/dielectric stack for insulation purposes. A lowerend of slit structure can be in contact with a doped region.

Method 600A proceeds to operation 614, in which a plurality of TACs areformed through the alternating dielectric stack. TACs can be formed inthe one or more inside regions by first etching vertical openings (e.g.,by wet etching and/or dry etching), followed by filling the openingswith conductive materials using ALD, CVD, PVD, any other suitableprocesses, or any combination thereof. The conductive materials used forfilling the local contacts can include, but are not limited to, W, Co,Cu, Al, polysilicon, silicides, or any combination thereof. In someembodiments, other conductive materials are also used to fill theopenings to function as a barrier layer, an adhesion layer, and/or aseed layer.

TACs can be formed by etching through the entire thickness of thealternating dielectric stack. Because the alternating dielectric stackincludes alternating layers of dielectrics, such as silicon oxide andsilicon nitride, the openings of TACs can be formed by deep etching ofdielectric materials (e.g., by deep reactive-ion etching (DRIE) processor any other suitable anisotropic etch process). In some embodiments,although TACs are formed after the gate replacement, by reserving anarea of the alternating dielectric stack that is not affected by thegate replacement process (not turned into alternatingconductor/dielectric stack), TACs can be formed through dielectriclayers (without passing through any conductive layers), which simplifiesthe fabrication process and reduces cost.

Method 600A proceeds to operation 616, in which an array interconnectionlayer is formed on the alternating stack. The array interconnectionlayer can be used to transfer electrical signals between the TACs andother parts of the 3D memory device, such as the peripheral circuits. Insome embodiments, fabrication processes to form the arrayinterconnection layer include forming a dielectric layer followed byforming a plurality of interconnection structures. One or more of theinterconnection structures can be in contact with the TACs,respectively.

The dielectric layer can include one or more layers of dielectricmaterials including, but not limited to, silicon oxide, silicon nitride,silicon oxynitride, or any combination thereof. The interconnectionstructures can include, but are not limited to, contacts,single-layer/multi-layer vias, conductive lines, plugs, pads, and/or anyother suitable conductive structures including, but not limited to, W,Co, Cu, Al, doped silicon, silicides, or any combination thereof.

In some embodiments, fabrication processes to form the interconnectionstructures include forming openings in the dielectric layer followed byfilling the openings with conductive materials. The openings in thedielectric layer can be filled with conductive materials by ALD, CVD,PVD, any other suitable processes, or any combination thereof. In someembodiments, fabrication processes to form the interconnectionstructures further include forming one or more conductive layers and oneor more contact layers in the dielectric layer. The conductive layersand the conductor contact layers can be formed by any suitable knownBEOL methods.

Referring to FIG. 6B, a flowchart of an exemplary method 600B forforming a peripheral circuit and a peripheral interconnection layer isillustrated, according to some embodiments. As shown in FIG. 6B, method600B starts at operation 622, in which a peripheral circuit is formed ona second substrate. In some embodiments, the second substrate can be anysuitable semiconductor substrate having any suitable structure, such asa monocrystalline single-layer substrate, a polycrystalline silicon(polysilicon) single-layer substrate, a polysilicon and metalmulti-layer substrate, etc.

The peripheral circuit can include any suitable peripheral device formedon the second substrate and any suitable interconnection circuitsbetween the peripheral device. One or more peripheral devices and/orinterconnection circuits can be formed by a plurality of processingsteps including, but not limited to, photolithography, dry/wet etch,thin film deposition, thermal growth, implantation, CMP, or anycombination thereof.

Method 600B proceeds to operation 624, in which a peripheralinterconnection layer is formed on the peripheral circuit. Theperipheral interconnection layer can include a dielectric layer abovethe peripheral circuit and one or more interconnection structures formedin the dielectric layer. The dielectric layer can include one or morelayers of dielectric materials such as silicon oxide, silicon nitride,silicon oxynitride, or any combination thereof. The interconnectionstructures can include, but are not limited to, contacts,single-layer/multi-layer vias, conductive lines, plugs, pads, and/or anyother suitable conductive structures including, but not limited to, W,Co, Cu, Al, doped silicon, silicides, or any combination thereof.

In some embodiments, the interconnection structures can be formed byusing any suitable known middle-end-of-line (MEOL) method. For example,fabrication processes to form the interconnection structures can includeforming openings in the dielectric layer followed by filling theopenings with conductive materials. The openings in the dielectric layercan be filled with conductive materials by ALD, CVD, PVD, any othersuitable processes, or any combination thereof. Further, fabricationprocesses to form the interconnection structures can include forming oneor more conductive layers and one or more contact layers in thedielectric layer. The conductive layers and the contact layers caninclude conductor materials deposited by one or more thin filmdeposition processes including, but not limited to, CVD, PVD, ALD,electroplating, electroless plating, or any combination thereof.Fabrication processes to form the conductive layer and contact layerscan include photolithography, CMP, wet/dry etch, or any combinationthereof.

Method 600B proceeds to operation 626, in which the array device (andthe array interconnection layer) is positioned (or otherwise disposed)below the first substrate (e.g., by flipping the first substrate upsidedown), and the array interconnection layer is aligned with theperipheral interconnection layer.

Method 600B proceeds to operation 628, in which the arrayinterconnection layer is joined with the peripheral interconnectionlayer. The array interconnection layer can be joined with the peripheralinterconnection layer by flip-chip bonding the first and secondsubstrates. In some embodiments, the array interconnection layer and theperipheral interconnection layer are joined by hybrid bonding of thefirst substrate and the second substrate in a face-to-face manner, suchthat the array interconnection layer is above and in contact with theperipheral interconnection layer in the resulting 3D memory device.

Hybrid bonding (also known as “metal/dielectric hybrid bonding”) can bea direct bonding technology (e.g., forming bonding between surfaceswithout using intermediate layers, such as solder or adhesives), whichobtains metal-metal bonding and dielectric-dielectric bondingsimultaneously.

Method 600B proceeds to operation 630, in which the first substrate isthinned so that the thinned first substrate serves as a semiconductorlayer above the array device (e.g., the NAND strings).

Method 600B proceeds to operation 632, in which a BEOL interconnectionlayer can be formed above the semiconductor layer.

FIG. 7 depicts a schematic enlarged plan view of a region 270 shown inFIG. 2 including a portion of a memory finger 242 isolated by slitstructures 214 and including a plurality of channel structures 212(i.e., channel hole 300 as shown in FIG. 3 ) and a top select gate (TSG)cut 255, according to some embodiments of the present disclosure.

As shown in FIG. 7 , region 700 of 3D memory device 100 (i.e., region270 as shown in FIG. 2 ) can include a plurality of bitlines (BL) 702a-702 d extending along the BL direction perpendicular to a memoryfinger 742 (i.e., memory finger 242 as shown in FIG. 2 ) and spacedhorizontally along the WL direction. The plurality of bitlines (BL) 702a-702 d are each connected to a top end of a plurality of channel holes704 a-704 h (e.g., channel hole 300 as shown in FIG. 3 ), respectively,to form a plurality of memory strings. Each bitline 702 a-702 d can beconnected to two channel holes 704 a-704 h, respectively. For example,first bitline 702 a can be connected to channel holes 704 a, 704 dseparated spatially by a top select gate (TSG) cut 755 (i.e., TSG cut255 as shown in FIG. 2 ). In some embodiments, channel holes 704 a-704 hcan each be a plurality of vertical memory strings. In some embodiments,channel holes 704 a-704 h can each be a vertical memory string of aplurality of memory cells.

Channel holes 704 a-704 h are arranged in vertical columns spaced alongthe WL direction. Channel hole pitch 706 includes a first verticalcolumn of channel holes 704 a-704 d, a second vertical column of channelholes 704 e-704 h, and bitlines 702 a-702 d (i.e., four bitlines (BL)).Channel hole pitch 706 defines a horizontal distance (i.e., along the WLdirection) of a repeating pattern of channel holes, for example, twocolumns of channel holes. Channel hole pitch 706 is defined or limitedby a channel hole manufacturing process (e.g., photolithographyprocess).

Memory finger 742 is isolated from adjacent memory fingers by slitstructures 714 (i.e., slit structure 214 as shown in FIG. 2 ). Memoryfinger 742 can include a first memory page 708 a and a second memorypage 708 b. First memory page 708 a can include channel holes 704 a, 704b, 704 e, 704 f. Second memory page 708 b can include channel holes 704c, 704 d, 704 g, 704 h. As shown in FIG. 7 , a center row of channelholes can be cut through by top select gate (TSG) cut 755 (e.g., topthree wordline (WL) layers) in order to individually select first orsecond memory pages 708 a, 708 b during write and read operations of 3Dmemory device 100. Memory finger 742 requires two reads to retrieve datafrom channel holes 704 a-704 h, since each bitline is connected to twochannel holes.

Top select gate (TSG) cut 755 occupies a semiconducting (e.g., silicon)area of memory finger 742, but is not used for data storage. The use oftop select gate (TSG) cut 755 increases the overall memory finger 742size (i.e., along BL direction) and lowers the effective bit density ofmemory finger 742. Hence, top select gate (TSG) cut 755 increases memoryblock 115 size and 3D memory device 100 size. Further, overall memorypage 708 a, 708 b size (i.e., along WL direction) is limited by bitlinepitch 705, which is limited by channel hole pitch 706. As shown in FIG.7 , four bitlines 702 a-702 d are connected to four channel holes perpage and, thus, bitline pitch 705 is 0.25 times channel hole pitch 706.A larger memory finger size typically requires longer wordline (WL)connections, which leads to larger wordline (WL) time constants andslower read and total programming times for 3D memory device 100.

FIGS. 8A, 8B, and 9 illustrate schematic enlarged plan views of a region(e.g., region 270 shown in FIG. 2 ) of exemplary 3D memory devices,according to some embodiments of the present disclosure. FIGS. 8A, 8B,and 9 are similar to FIG. 7 . FIGS. 8A, 8B, and 9 illustrate alternativeembodiments of the memory architecture depicted in region 700 of FIG. 7with a higher bit density, smaller channel hole pitch, and omitted topselect gate (TSG) cut for larger memory page size, faster read andprogramming times, and smaller overall memory block and 3D memory devicesize.

As shown in FIG. 8A, a region 800A of exemplary 3D memory device 800(i.e., similar to region 700 as shown in FIG. 7 for 3D memory device100) can include a plurality of bitlines (BL) 802 a-802 h extendingalong the BL direction perpendicular to a memory finger 842 (i.e.,similar to memory finger 742 as shown in FIG. 7 ) and spacedhorizontally along the WL direction. FIG. 8B illustrates region 800A of3D memory device 800 as shown in FIG. 8A with bitlines (BL) 802 a-802 homitted for clarity.

As shown in FIGS. 8A-8B, 3D memory device 800 includes a plurality ofchannel holes 804 a-804 h spaced relative to each along the wordline(WL) direction. The plurality of bitlines (BL) 802 a-802 h are eachconnected to a top end of the plurality of channel holes 804 a-804 h,respectively, to form a plurality of memory strings. As shown in FIG.8A, each bitline 802 a-802 h can be connected to an individual channelhole 804 a-804 h, respectively. For example, first bitline 802 a can beconnected to channel hole 804 a, second bitline 802 b can be connectedto channel hole 804 b, and so on. Top select gate (TSG) cut is omittedin 3D memory device 800, and all channel holes 804 a-804 h can be readwith a single page read. In some embodiments, channel holes 804 a-804 hcan each be a plurality of vertical memory strings. In some embodiments,channel holes 804 a-804 h can each be a vertical memory string of aplurality of memory cells.

In some embodiments, channel holes 804 a-804 h can be displaced evenlyrelative to each other along the wordline (WL) direction. In someembodiments, channel holes 804 a-804 h can be displaced evenly from eachother by a relative distance of about 10 nm to 50 nm. For example, acenter of channel hole 804 a can be displaced from a center of channelhole 804 b by about 10 nm to 50 nm. In some embodiments, channel holes804 a-804 h can be displaced evenly from each other by a relativedistance of about 1 nm to 10 nm. For example, a center of channel hole804 a can be displaced from a center of channel hole 804 b by about 1 nmto 10 nm.

Channel holes 804 a-804 h are arranged in vertical columns spaced alongthe WL direction, with each vertical column angled relative to the BLdirection. Channel hole pitch 806 includes a first column of channelholes 804 a-804 d, a second column of channel holes 804 e-804 h, firstcolumn angle 810, second column angle 812, and bitlines 802 a-802 h(i.e., eight bitlines (BL)). Each channel hole 804 a-804 h can bedisplaced evenly along the WL direction in order for each individualbitline 802 a-802 h to connect to each channel hole 804 a-804 h,respectively. In some embodiments, first column of channel holes 804a-804 d can be angled to first column angle 810 relative to the BLdirection, and second column of channel holes 804 e-804 h can be angledto second column angle 812 relative to the BL direction. For example,first and second column angles 810, 812 can be about 5 to about 30degrees. For example, first and second column angles 810, 812 can beabout 10 to about 15 degrees. In some embodiments, first and secondcolumn angles 810, 812 can be equal. In some embodiments, first andsecond column angles 810, 812 can be different.

Memory finger 842 is isolated from adjacent memory fingers by slitstructures 814 (i.e., similar to slit structure 214 as shown in FIG. 2). Memory finger 842 can include memory page 808 with channel holes 804a-804 h. As shown in FIG. 8B, TSG cut is omitted and as a result overallmemory finger 842 size (i.e., along BL direction) is reduced, whichincreases the effective bit density of memory finger 842. Hence, memorypage 808 size doubles (as compared to the memory architecture shown inFIG. 7 ), and overall memory block size and 3D memory device 800 sizeare reduced. Further, as shown in FIG. 8A, eight bitlines 802 a-802 hare connected to eight channel holes 804 a-804 h per page and, thus,bitline pitch 805 is 0.125 times channel hole pitch 806. The reducedbitline pitch 805 can be achieved by alignment manufacturing processes,for example, quadruple lithographic patterning. The displacement ofchannel holes 804 a-804 h also allows for a greater alignment marginbetween bitline 802 a-802 h and channel hole 804 a-804 h connections,respectively. 3D memory device 800 provides a larger memory page 808size and bit density (i.e., one page read for eight channel holes due toindividual bitline connections), smaller memory finger 842 size (i.e.,due to omission of top select gate (TSG) cut), and faster read andprogramming times due to lower wordline (WL) time constants. TSG iscontinuous along the BL direction of memory page 808 of memory finger842 between slit structures 814 and connects to channel holes 804 a-804h.

Referring to FIG. 9 , a region 900A of exemplary 3D memory device 900(i.e., similar to region 700 as shown in FIG. 7 for 3D memory device100) can include a plurality of bitlines (BL) 902 a-902 j extendingalong the BL direction perpendicular to a memory finger 942 (i.e.,similar to memory finger 742 as shown in FIG. 7 ) and spacedhorizontally along the WL direction.

As shown in FIG. 9 , 3D memory device 900 includes a plurality ofchannel holes 904 a-904 j spaced relative to each along the WLdirection. The plurality of bitlines (BL) 902 a-902 j are each connectedto a top end of the plurality of channel holes 904 a-904 j,respectively, to form a plurality of memory strings. As shown in FIG. 9, each bitline 902 a-902 j can be connected to an individual channelhole 904 a-904 j, respectively. For example, first bitline 902 a can beconnected to channel hole 904 a, second bitline 902 b can be connectedto channel hole 904 b, and so on. Top select gate (TSG) cut is omittedin 3D memory device 900, and all channel holes 904 a-904 j can be readwith a single page read. In some embodiments, channel holes 904 a-904 jcan each be a plurality of vertical memory strings. In some embodiments,channel holes 904 a-904 j can each be a vertical memory string of aplurality of memory cells.

In some embodiments, channel holes 904 a-904 j can be displaced evenlyrelative to each other along the wordline (WL) direction. In someembodiments, channel holes 904 a-904 j can be displaced evenly from eachother by a relative distance of about 10 nm to 50 nm. For example, acenter of channel hole 904 a can be displaced from a center of channelhole 904 b by about 10 nm to 50 nm. In some embodiments, channel holes904 a-904 j can be displaced evenly from each other by a relativedistance of about 1 nm to 10 nm. For example, a center of channel hole904 a can be displaced from a center of channel hole 904 b by about 1 nmto 10 nm.

Channel holes 904 a-904 j are arranged in vertical columns spaced alongthe WL direction, with each vertical column angled relative to the BLdirection. Channel hole pitch 906 includes a first column of channelholes 904 a-904 e, a second column of channel holes 904 f-904 j, firstcolumn angle 910, second column angle 912, and bitlines 902 a-902 j(i.e., ten bitlines (BL)). Each channel hole 904 a-904 j can bedisplaced evenly along the WL direction in order for each individualbitline 902 a-902 j to connect to each channel hole 904 a-904 j,respectively. In some embodiments, first column of channel holes 904a-904 e can be angled to first column angle 910 relative to the BLdirection, and second column of channel holes 904 e-904 j can be angledto second column angle 912 relative to the BL direction. For example,first and second column angles 910, 912 can be about 5 to about 30degrees. For example, first and second column angles 910, 912 can beabout 10 to about 15 degrees. In some embodiments, first and secondcolumn angles 910, 912 can be equal. In some embodiments, first andsecond column angles 910, 912 can be different.

Memory finger 942 is isolated from adjacent memory fingers by slitstructures 914 (i.e., similar to slit structure 214 as shown in FIG. 2). Memory finger 942 can include memory page 908 with channel holes 904a-904 j. As shown in FIG. 9 , TSG cut is omitted and as a result overallmemory finger 942 size (i.e., along BL direction) is reduced, whichincreases the effective bit density of memory finger 942. Hence, memorypage 908 size is increased by a factor of 2.5 (as compared to the memoryarchitecture shown in FIG. 7 ), and overall memory block size and 3Dmemory device 900 size are reduced. Further, as shown in FIG. 9 , tenbitlines 902 a-902 j are connected to ten channel holes 904 a-904 j perpage and, thus, bitline pitch 905 is 0.1 times channel hole pitch 906.The reduced bitline pitch 905 can be achieved by alignment manufacturingprocesses, for example, quadruple lithographic patterning. Thedisplacement of channel holes 904 a-904 j also allows for a greateralignment margin between bitline 902 a-902 j and channel hole 904 a-904j connections, respectively. 3D memory device 900 provides a largermemory page 908 size and bit density (i.e., one page read for tenchannel holes due to individual bitline connections), smaller memoryfinger 942 size (i.e., due to omission of top select gate (TSG) cut),and faster read and programming times due to lower wordline (WL) timeconstants. TSG is continuous along the BL direction of memory page 908of memory finger 942 between slit structures 914 and connects to channelholes 904 a-904 j.

In some embodiments, memory finger 942 can include twelve bitlines 902in channel hole pitch 906, with each bitline 902 connected to anindividual channel hole 904. For example, memory page 908 size can betripled (as compared to the memory architecture shown in FIG. 7 ), andtwelve bitlines 902 can be connected to twelve channel holes 904 perpage and, thus, bitline pitch 905 can be 0.083 times channel hole pitch906.

Referring to FIG. 10 , a schematic flowchart of an exemplary method forforming an exemplary memory finger for a 3D memory device isillustrated, according to some embodiments of the present disclosure. Itshould be understood that the operations shown in FIGS. 6A-6B are notexhaustive and that other operations can be performed as well before,after, or between any of the illustrated operations.

As shown in FIG. 10 , method 1000 starts at operation 1002, in which analternating layer stack is formed on a first substrate that includes analternating conductor/dielectric stack including a plurality ofconductor/dielectric pairs. The process is similar to that described inmethod 600A as shown in FIG. 6A. In some embodiments, the firstsubstrate can be any suitable semiconductor substrate having anysuitable structure, such as a monocrystalline single-layer substrate, apolycrystalline silicon (polysilicon) single-layer substrate, apolysilicon and metal multi-layer substrate, etc. A plurality ofconductor/dielectric pairs (also referred to herein as an “alternatingconductor/dielectric stack”) can be formed on the first substrate. Thealternating conductor/dielectric stack can be formed by one or more thinfilm deposition processes including, but not limited to, chemical vapordeposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), or any combination thereof.

Method 1000 proceeds to operation 1004, in which a plurality of slitstructures are formed with each extending vertically through thealternating conductor/dielectric stack and laterally along a wordlinedirection to divide the alternating conductor/dielectric stack into atleast one memory finger. The process is similar to that described inmethod 600A as shown in FIG. 6A.

Method 1000 proceeds to operation 1006, in which a first column ofchannel holes and a second column of channel holes are formed in the atleast one memory finger. The process is similar to that described inmethod 600A as shown in FIG. 6A. However, the channel holes of the firstand second columns are displaced relative to each other along thewordline direction. Each channel hole can extend through the alternatingconductor/dielectric stack.

In some embodiments, channel holes can be displaced evenly relative toeach other along the wordline direction. For example, channel holes canbe displaced by a relative distance of about 1 nm to 10 nm. For example,channel holes can be displaced by a relative distance of about 10 nm to50 nm.

In some embodiments, fabrication processes to form the channel holesinclude forming a channel hole that extends vertically through thealternating conductor/dielectric stack by, for example, wet etchingand/or dry etching. In some embodiments, fabrication processes to formthe channel holes further include forming a semiconductor channel and amemory film between the semiconductor channel and theconductor/dielectric pairs in the alternating conductor/dielectricstack. The semiconductor channel can include semiconductor materials,such as polysilicon. The memory film can be a composite dielectriclayer, such as a combination of a tunneling layer, a storage layer, anda blocking layer. The tunneling layer can include dielectric materialsincluding, but not limited to, silicon oxide, silicon nitride, siliconoxynitride, or any combination thereof. Electrons or holes from thesemiconductor channel can tunnel to a storage layer through thetunneling layer. The storage layer can include materials for storingcharge for memory operation. The storage layer materials include, butare not limited to, silicon nitride, silicon oxynitride, a combinationof silicon oxide and silicon nitride, or any combination thereof. Theblocking layer can include dielectric materials including, but notlimited to, silicon oxide or a combination of silicon oxide/siliconnitride/silicon oxide (ONO). The blocking layer can further include ahigh-k dielectric layer, such as an aluminum oxide (Al₂O₃) layer.Semiconductor channel and memory film can be formed by one or more thinfilm deposition processes, such as ALD, CVD, PVD, any other suitableprocesses, or any combination thereof.

Method 1000 proceeds to operation 1008, in which a plurality of bitlinesin the at least one memory finger are formed. Each bitline is connectedto an individual channel hole. In some embodiments, the plurality ofbitlines can be formed by a lithographic process. For example, theplurality of bitlines can be formed by quadruple patterning.

In some embodiments, the plurality of bitlines can be formed to have abitline pitch that is 0.125 times the channel hole pitch. In someembodiments, the plurality of bitlines can be formed to have a bitlinepitch that is 0.1 times the channel hole pitch. In some embodiments, theplurality of bitlines can be formed to have a bitline pitch that is0.083 times the channel hole pitch.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the present disclosure that others can, byapplying knowledge within the skill of the art, readily modify and/oradapt for various applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent disclosure. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

Embodiments of the present disclosure have been described above with theaid of functional building blocks illustrating the implementation ofspecified functions and relationships thereof. The boundaries of thesefunctional building blocks have been arbitrarily defined herein for theconvenience of the description. Alternate boundaries can be defined solong as the specified functions and relationships thereof areappropriately performed.

The Summary and Abstract sections may set forth one or more but not allexemplary embodiments of the present disclosure as contemplated by theinventor(s), and thus, are not intended to limit the present disclosureand the appended claims in any way.

The breadth and scope of the present disclosure should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A method for forming a memory finger in athree-dimensional memory device, comprising: forming, on a substrate, analternating layer stack; forming a plurality of slit structures eachextending vertically through the alternating layer stack and laterallyalong a wordline direction to divide the alternating layer stack into atleast one memory finger; forming, in the alternating layer stack, aplurality of conductor/dielectric layer pairs; forming a first column ofvertical memory strings extending through the alternating layer stack inthe at least one memory finger, wherein the vertical memory strings inthe first column are displaced relative to each other along the wordlinedirection; forming a second column of vertical memory strings extendingthrough the alternating layer stack in the at least one memory finger,wherein the vertical memory strings in the second column are displacedrelative to each other along the wordline direction; and forming aplurality of bitlines displaced along the wordline direction andextending along a bitline direction in the at least one memory finger,wherein each bitline is connected to an individual vertical memorystring in the first and second columns.
 2. The method of claim 1,wherein forming the plurality of bitlines comprises quadruple patterningthe plurality of bitlines.
 3. The method of claim 1, wherein: formingthe vertical memory strings of the first column comprises evenlydisplacing the vertical memory strings of the first column relative toeach other along the wordline direction; and forming the vertical memorystrings of the second column comprises evenly displacing the verticalmemory strings of the second column relative to each other along thewordline direction.
 4. The method of claim 3, wherein: the verticalmemory strings of the first column are displaced relative to each otherby a relative distance of about 1 nm to about 10 nm; and the verticalmemory strings of the second column are displaced relative to each otherby a relative distance of about 1 nm to about 10 nm.
 5. The method ofclaim 1, further comprising forming a continuous top select gate alongthe bitline direction and connected to the first and second columns ofvertical memory strings in the at least one memory finger.
 6. The methodof claim 1, wherein: forming the first column of vertical memory stringscomprises forming the first column of vertical memory strings along afirst angle relative to the bitline direction; and forming the secondcolumn of vertical memory strings comprises forming the second column ofvertical memory strings along a second angle relative to the bitlinedirection.
 7. The method of claim 6, wherein forming the first andsecond columns of vertical memory strings comprises arranging the firstand second angles to be equal.
 8. The method of claim 6, wherein formingthe first and second columns of vertical memory strings comprisesarranging the first and second angles to be different.
 9. The method ofclaim 6, wherein: forming the first column of vertical memory stringscomprises forming at least four vertical memory strings within the atleast one memory finger and along the first angle; and forming thesecond column of vertical memory strings comprises forming at least fourvertical memory strings within the at least one memory finger and alongthe second angle.
 10. The method of claim 6, wherein forming the secondcolumn of vertical memory strings comprises offsetting the second columnof vertical memory strings along the bitline direction relative to thefirst column of vertical memory strings, such that each vertical memorystring of the second column of vertical memory strings is disposedbetween adjacent vertical memory strings of the first column of verticalmemory strings along the bitline direction.
 11. A method for forming amemory finger in a three-dimensional memory device, comprising: forminga first column of memory cells extending through an alternating layerstack, wherein the memory cells of the first column are displacedrelative to each other along a wordline direction; forming a secondcolumn of memory cells extending through the alternating layer stack,wherein the memory cells in the second column are displaced relative toeach other along the wordline direction; and forming a plurality ofbitlines displaced along the wordline direction and extending along abitline direction, wherein each bitline is connected to an individualmemory cell in the first and second columns, wherein the first andsecond columns of memory cells are formed within a memory finger. 12.The method of claim 11, wherein forming the second column of memorycells comprises offsetting the second column of memory cells along thebitline direction relative to the first column of memory cells, suchthat each memory cell of the second column of memory cells is disposedbetween adjacent memory cells of the first column of memory cells alongthe bitline direction.
 13. The method of claim 11, wherein: forming thefirst and second columns of memory cells comprises defining a channelhole pitch along the wordline direction.
 14. The method of claim 13,wherein forming the first and second columns of memory cells comprisesarranging the channel hole pitch between the first and second columns ofmemory cells along the wordline direction to be less than
 1. 15. Themethod of claim 11, wherein: forming first and second columns of memorycells comprises defining a channel hole pitch along the wordlinedirection; and forming the plurality of bitlines comprises defining abitline pitch along the bitline direction.
 16. The method of claim 15,wherein forming the first and second columns of memory cells and theplurality of bitlines comprises arranging the channel hole pitch to begreater than ten times the bitline pitch.
 17. The method of claim 11,wherein: forming the first column of memory cells comprises forming thefirst column of memory cells along a first angle relative to the bitlinedirection; and forming the second column of memory cells comprisesforming the second column of memory cells along a second angle relativeto the bitline direction.
 18. The method of claim 17, wherein: formingthe first column of memory cells comprises forming at least four memorycells within the memory finger and along the first angle; and formingthe second column of memory cells comprises forming at least four memorycells within the memory finger and along the second angle.
 19. Themethod of claim 18, wherein: forming the first column of memory cellscomprises forming at least five memory cells within the memory fingerand along the first angle; and forming the second column of memory cellscomprises forming at least five memory cells within the memory fingerand along the second angle.
 20. The method of claim 19, wherein: formingthe first column of memory cells comprises forming six memory cellswithin the memory finger and along the first angle; and forming thesecond column of memory cells comprises forming six memory cells withinthe memory finger and along the second angle.